springboot Unable to assert JSON keys with dot in it with JsonContentAssert (spring-boot-test:2.2.6-RELEASE)

Unable to assert JSON keys with dot in it with JsonContentAssert (spring-boot-test:2.2.6-RELEASE).

Example: I have a valid JSON data as:

{
    "first.name": "sa"
}

If I try asserting the JSON path $['first.name'] or $.['first.name'] it should pass. However I am getting error